Effects of Ho_2O_3 addition on defects of BaTiO_3

摘要

Effects of Ho_2O_3 addition on defects of BaTiO_3 ceramic have been studied in terms of electrical conductivity at 1200℃ as a function of oxygen partial pressure (P°_(O_2)) and oxygen vacancy concentration. The substitution of Ho~(3+) for the Ti site in Ba(Ti_(1-x)Ho_x)O_(3-0.5x) resulted in a significant shift of conductivity minimum toward lower oxygen pressures and showed an acceptor-doped behavior. The solubility limit of Ho on Ti sites was confirmed less than 3.0 mol% by measuring the electrical conductivity and the lattice constant. Oxygen vacancy concentrations were calculated from the positions of P°_(O_2) in the conductivity minima and were in good agreement with theoretically estimated values within the solubility limit. The Curie point moved to lower temperatures with increasing the oxygen vacancy concentration and Ho contents.